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gs¼Ä´æÆ÷µÄµØ·½´æµÄÊÇdo_page_faultµÄµØÖ·£¬¶øÏÂÃæµÄ×¢ÊÍҲ˵ÁËÕâ¸öÇé¿ö¡£Èç¹ûÓû§½ø³ÌʹÓÃÁËgs¼Ä´æÆ÷£¬·µ»ØµÄʱºò²»ÊÇÎÞ·¨»Ö¸´ÁËÂð¡£²»½öÊÇÕâÀϵͳµ÷ÓõÄʱºòҲûÓб£´ægsENTRY(page_fault)
RING0_EC_FRAME
ASM_CLAC
pushl_cfi $do_page_fault
ALIGN
error_code:
/* the function address is in %gs's slot on the stack */
pushl_cfi %fs
/*CFI_REL_OFFSET fs, 0*/
pushl_cfi %es
/*CFI_REL_OFFSET es, 0*/
pushl_cfi %ds
/*CFI_REL_OFFSET ds, 0*/
pushl_cfi %eax
CFI_REL_OFFSET eax, 0
pushl_cfi %ebp
CFI_REL_OFFSET ebp, 0
pushl_cfi %edi
CFI_REL_OFFSET edi, 0
pushl_cfi %esi
CFI_REL_OFFSET esi, 0
pushl_cfi %edx
CFI_REL_OFFSET edx, 0
pushl_cfi %ecx
CFI_REL_OFFSET ecx, 0
pushl_cfi %ebx
CFI_REL_OFFSET ebx, 0
¶ÑÕ»ÖÐÔ±¾ÓÃÓÚ´æ·ÅgsµÄslotÖ»ÊÇÁÙʱÓÃÀ´´æ·ÅÒ»ÏÂdo_page_faultµÄµØÖ·£¬gsµÄÄÚÈݺóÃ滹ÊÇͨ¹ýecx¼Ä´æÆ÷£¬ÖØзÅÈë¸ÃλÖÃÁË¡£
error_code:
/* the function address is in %gs's slot on the stack */
pushl_cfi %fs
/*CFI_REL_OFFSET fs, 0*/
pushl_cfi %es
/*CFI_REL_OFFSET es, 0*/
pushl_cfi %ds
/*CFI_REL_OFFSET ds, 0*/
pushl_cfi %eax
CFI_REL_OFFSET eax, 0
pushl_cfi %ebp
CFI_REL_OFFSET ebp, 0
pushl_cfi %edi
CFI_REL_OFFSET edi, 0
pushl_cfi %esi
CFI_REL_OFFSET esi, 0
pushl_cfi %edx
CFI_REL_OFFSET edx, 0
pushl_cfi %ecx
CFI_REL_OFFSET ecx, 0
pushl_cfi %ebx
CFI_REL_OFFSET ebx, 0
cld
movl $(__KERNEL_PERCPU), %ecx
movl %ecx, %fs
UNWIND_ESPFIX_STACK
# ½«gs±£´æµ½ecx¼Ä´æÆ÷ÖÐ
GS_TO_REG %ecx
# ½«¶ÑÕ»ÖÐÔ±¾´æ·Ågs´¦µÄÄÚÈÝ(ÏÖÔÚÊÇÒì³£´¦Àíº¯Êýdo_page_faultµÄµØÖ·)£¬±£´æµ½ediÖÐ
movl PT_GS(%esp), %edi # get the function address
movl PT_ORIG_EAX(%esp), %edx # get the error code
movl $-1, PT_ORIG_EAX(%esp) # no syscall to restart
# ½«ecxÖеÄÄÚÈÝ·ÅÈëµ½gs(%esp)ÖУ¬´ËʱecxÖб£´æµÄÊÇÔgsµÄÄÚÈÝ
REG_TO_PTGS %ecx
# ÉèÖÃgsÄÚÈÝΪ__KERNEL_STACK_CANARY(ÓëgccµÄstack protectorÏà¹Ø£¬Î´¿ªÆô´Ë¹¦ÄܵĻ°£¬Êµ¼ÊΪ0)
SET_KERNEL_GS %ecx
# È¡__USER_DS£¬·ÅÈëdsºÍesÖÐ
movl $(__USER_DS), %ecx
movl %ecx, %ds
movl %ecx, %es
TRACE_IRQS_OFF
movl %esp,%eax # pt_regs pointer
# µ÷ÓÃÒì³£´¦ÀíºÍº¯Êý
call *%edi
# Òì³£·µ»Ø
jmp ret_from_exception
CFI_ENDPROC
END(page_fault)
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